In the semiconductor device including a copper interconnection, for decreasing a signal delay in the multi-level interconnection structure, low dielectric constant film is used as the inter-layer insulating film. As the barrier film for preventing the diffusion of copper into the inter-layer insulating film, metal film containing refractory metal, such as tantalum, titanium or others, or its nitride is used.
However, as the interconnection trench and the via-hole are downsized and the dielectric constant of the inter-layer insulating films is lowered due to downsizing of the semiconductor device, it is difficult to ensure the reliability of the barrier film by the degradation of the barrier ability of the barrier film under the influence of the degradation of the coverage of the barrier film at the trench part and the oxidation of the barrier film by the low dielectric constant insulating film. In such background, recently, as a technique for improving the reliability of the copper interconnection, the technique of forming the barrier film of the alloy of copper as the base metal and manganese (Mn) (Mn alloy material) is proposed. In the technique of forming the new barrier compound film of the Mn alloy material, an additive alloy element (Mn) is introduced in an interconnection layer, and thermal processing is made, whereby a layer having the diffusion preventing function is formed at the interface between the conductive part and the inter-layer insulating film by self-restore or self-alignment. Thus, the adhesion and barrier ability at the interface are ensured, and the reliability of the copper interconnection can be improved.
The following are examples of related: Japanese Laid-open Patent Publication No. 2005-277390; Japanese Laid-open Patent Publication No. 2008-205177; Haneda et al., “Self-Restored Barrier using Cu—Mn Alloy”, ADMETA, Vol. 124, pp. 27-28, 2007; Kudo et al., “Further Enhancement of Electro-migration Resistance by Combination of Self-aligned Barrier and Copper Wiring Encapsulation Techniques for 32-nm Nodes and Beyond”, International Interconnect Technology Conference, 2008, pp. 117-119; and Kudo et al., “Copper Wiring Encapsulation at Semi-Global Level to Enhance Wiring and Dielectric Reliabilities for Next-Generation Technology Nodes”, International Interconnect Technology Conference, 2009, pp. 188-190.
Mn added to the interconnection layer diffuses in the interconnection layer and is consumed out of the interconnection layer by the reaction of forming at the interface with the inter-layer insulating film a composite barrier compound layer containing a refractory metal material of the barrier layer, oxygen from the inter-layer insulating film, and the Mn. However, by this technique of adding Mn in the interconnection layer, excessive Mn which does not contribute to the reaction of forming the composite barrier compound layer resides in the interconnection or the via to resultantly increase the interconnection resistance and the contact resistance.